The present invention relates to a hollow profile, in particular crane girder for a crane, wherein the hollow profile has a cavity and an outer wall bounding the cavity, and at least one fastening element protruding from the outer wall for the, preferably re-releasable, fastening of at least one add-on part to the hollow profile. Furthermore, the invention relates to a crane with at least one hollow profile, and to a method for fastening an add-on part to a hollow profile.
Hollow profiles are frequently used in steel construction, in particular in the construction of cranes. An example for hollow profiles used in cranes is crane girders which are generally designed as a hollow profile in what is referred to as a box structure. The hollow profile has a cavity and an outer wall surrounding said cavity. The outer walls are generally comprised of flat or curved metal sheets which are welded to one another.
In order to prevent water from accumulating, in particular due to precipitation, in the cavity and to prevent corrosion of the outer walls starting from the cavity, hollow profiles are generally tightly welded. That is to say, the cavity of the hollow profile is sealed in relation to the surroundings or the atmosphere, and therefore water cannot penetrate the cavity.
In order to fasten add-on parts, for example running rails, ladders, etc., to the hollow profile, fastening elements are frequently welded to the outer side of the outer wall of the hollow profile. This has the advantage that the tightness of the hollow profile can be ensured in the operating state.
FIG. 1 shows an embodiment, known from the prior art, of the fastening of an add-on part 5 (in the form of a running rail for a trolley of a crane) to a hollow profile. Only one portion of the closed hollow profile 1 is illustrated. The fastening elements 4 (=welded rail clamps) protruding from the outer wall 3 are connected in an integrally bonded manner to the outer wall 3 by weld seams 29. By tightening a nut 22, the rail clamp 13 is pressed against the rail foot of the running rail in the operating state in order to clamp the add-on part 5. The mathematical determination of the strength of a component under dynamic stressing is decisively determined by the notch events which occur. Notches which are caused, for example, by the weld seams 29 have scarcely any effect on the stressability of a component in the event of static, i.e. predominantly resting, stressing. In the event of dynamic, i.e. predominantly non-resting, stressing (for example due to position-changeable loads of a trolley of a crane), notches can lead to cracking and to a progressive cross-sectional weakening of the hollow profile. In order nevertheless to be able to verify a sufficient strength of the hollow profile mathematically, structural measures, such as, for example, relatively great wall thicknesses in the region of the load introduction points, are necessary. The dead weight of the hollow profile and the driving power required for operating the crane increase as a result.